1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a stator vane with a mate face seal.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A gas turbine engine, such as a large frame heavy duty industrial gas turbine (IGT) engine, includes a turbine with one or more stages of stator vanes to guide a hot gas flow toward a downstream row of rotor blades. Stator vanes are typically made in segments with one or more airfoils extending between an outer shroud and an inner shroud. Because the turbine operates under a high temperature, thermal expansion of the stator vane segments requires a loose fit at the engine cold state so that any gaps are closed when the parts are at the high operating temperature.
FIG. 1 shows two stator vane segments each with a single airfoil 11 with a prior art vane mate-face cooling and sealing arrangement. The airfoil extends between endwalls 12 or shrouds and is attached to the engine through aft hooks 13. In the FIG. 1 vane mate-face design, there is no built-in scheme or any sealing arrangement to prevent hot gas ingression along an axial gap at a junction between two adjacent vane rails 14 as well as misalignment between two abutting vane end rails. FIG. 2 shows a detailed cross section view of the vane mate-face seal design for two adjacent mate-faces. Each mate-face includes a slot 15 in which a feather seal 16 is placed to seal a gap 17 between the two mate-faces. Impingement cavities 18 are formed on the top surface to provide impingement cooling for the endwalls. Metering holes 19 formed in an impingement plate 21 deliver cooling air to the impingement cavities 18 and then to the gap 17 to cool the mate-face and to purge hot gas flow from passing into the gap 17. A TBC (thermal barrier coating) 20 is applied on the hot gas side of the endwalls. FIG. 2 shows a riffle seal used to seal the mate face gap in a prior art turbine stator vane like FIG. 1.
As a result of the FIG. 1 structure, hot gas flows in and out along the mate-face gaps and creates an over-temperature at the vane rails corresponding to the hot gas injection location. In addition, use of a feather seal for the sealing mate-face gap will not provide for a good seal or alignment of the vanes. FIG. 3 shows the feather seal positioned against an upper surface of the slots due to the pressure acting on the feather seal from below. FIG. 4 shows the feather seal positioned against a lower surface of the slot due to pressure acting on the feather seal from above. FIG. 5 shows the feather seal out of alignment due to the two adjacent vane segments being out of alignment.